A dinuclear phosphite rhodium(I) complex obtained by syngas treatment of a Rh/hydroxy phosphonite olefin hydroformylation precatalyst

A hydroxy phosphonite was found to be unstable during the catalyst preformation routine applied towards a rhodium olefin hydroformylation catalyst. C—P bond cleavage occurred when the phosphonite was reacted with (acac)Rh(1,5‐COD)] (acac is acetyl acetate and 1,5‐COD is cycloocta‐1,5‐diene) at 80 °C and 20 bar of CO/H₂. As a result, a nearly planar six‐membered ring structure consisting of two rhodium(I) cations and two bridging phosphorous acid diester anions was formed, namely bisμ‐(4,8‐di‐tert‐butyl‐2,10‐dimethoxydibenzod,f]1,3,2]dioxaphosphepin‐6‐yl)oxy]‐1:2κ²P:O;1:2κ²O:P‐bis{6‐(1,1′‐biphenyl]‐2‐yloxy)‐4,8‐di‐tert‐butyl‐2,10‐dimethoxydibenzod,f]1,3,2]dioxaphosphepine‐κP]carbonylrhodium(I)} toluene tetrasolvate, Rh₂(C₂₂H₂₈O₅P)₂(C₃₄H₃₇O₅P)₂(CO)₂]·4C₇H₈. Further coordination of phosphite and of carbonyl groups resulted in 16‐electron rhodium centres.